Printed single-feed circularly polarized UHF reader antenna for RFID applications

In this paper an optimally designed corner trimmed microstrip UHF reader antenna fabricated using screen printing of silver ink on an FR4 substrate is presented. The reader antenna, 12×12 cm2 in size, is fed through a single microstip line with an SMA connector attached to the antenna board. The measured results demonstrate reflection coefficient better than −15 dB as well as 3dB-beamwidth greater than 60° over the 900 MHz–930 MHz frequency bandwidth. The measured axial ratio lower than 3 dB within the range of 910 MHz–920 MHz shows the antenna polarization is circular in this frequency range. The designed antenna is light, low-cost and easy to manufacture and therefore can be conveniently used as reader antenna in RFID retail monitoring applications.